Volatiles profiles and factors affecting absorption of key odorants in Osmanthus black tea

Abstract

Objectives: Osmanthus black tea (OBT) is produced by reprocessing black tea while it absorbs the fragrance of Osmanthus fragrans and this scenting process is crucial for forming the unique aroma of OBT. This work intended to reveal the effects of scenting parameters, the types of base tea, and scenting technologies on the aroma quality of OBT. Materials and Methods: In this study, volatile compounds of OBTs with different scenting parameters, types of base tea, and scenting technologies were analyzed by solid-phase microextraction and gas chromatography-mass spectrometry. Weighted gene co-expression network analysis and orthogonal partial least squares discriminant analysis were used to identify the key volatile compounds of OBT. Results: More than 80 volatile compounds of OBT were found, and six compounds, α-ionone, β-ionone, γ-decalactone, dihydro-β-ionone, dihydro-β-ionol, and 6-pentyl-2-pyrone, were identified as the key volatiles of OBT. As scenting time (ST) increased, the key volatile compounds in OBT showed an upward trend or increased initially and then decreased. Meanwhile, the contents of key volatile compounds increased as the ratio of flowers to tea (RFT) increased. In addition, base teas with a high proportion of pekoes produced higher-quality OBT by absorbing more key volatile compounds from O. fragrans. Comparing OBTs made from the fast-scenting process and the traditional scenting process (TS), showed that higher aroma quality was obtained through repeated scenting rounds of TS. Conclusions: Appropriate long ST and high RFT, as well as base tea with a high proportion of pekoes and TS with repeated scenting rounds are beneficial for the accumulation of odorants and the improvement of aroma quality in OBT.